Having some basic knowledge of Urdu

Main hamare ek problem. Jaisa ki ap ko malum hai ki ...(I cannt type urdu anymore) Urdu has two style of writting scripts, and also some place also use different Roman spelling(such as two "a" to symbolize "a"with "-", or kh to symbolize "x". I am confusing and even I download a Urdu input, with same spelling, I can see the urdu words is different formed. Why?